Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
  • F28D20/0056—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using solid heat storage material
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/14—Thermal energy storage

Definitions

• the present invention relates to ferrous alloys, and in particular ferrous alloys containing a proportion of free iron and having an enhanced resistance to oxidation at elevated temperatures, and to certain articles of manufacture constructed therefrom.
• Normal cast iron contains small proportions of carbon, phosphorus, silicon, manganese and traces of other elements. A part of the iron is present in a chemically combined form as carbide, silicide or phosphide and the bulk of the alloy consists of chemically free metallic iron, which may be alloyed with other metals.
• Metallurgists have hitherto taken great care to avoid the presence more than small quantities of phosphorus in cast iron or steels, since ferrous alloys containing more than about 0.20.5% by weight of phosphorus are known to be undesirably brittle and the brittleness is belived to increase with increasing phosphorus content.
• ferrous alloys have been recommended containing 0.5 to 1% by weight of phosphorus, but it has never been envisaged that an alloy of chemically free iron containing more than 1% by weight of phosphorus could usefully be employed in the construction of articles of manufacture.
• Our invention therefore provides articles of manufacture adapted for use in environments favouring high temperature oxidation of cast iron and constructed, at least in part, of an iron/phosphorus alloy comprising a major proportion of iron part of which is present as the chemically free metal, and from 2 to 15 by weight of phosphorus.
• a particularly preferred embodiment of our invention provides a storage heater comprising a thermal reservoir constructed at least in part of an iron/phosphorus alloy as aforesaid, means for supplying heat thereto, and means for withdrawing useful heat from the reservoir.
• inventions of our invention provide industrial or domestic boiler components, ingot moulds (parice ticularly ingot moulds for use with non-ferrous metals, such as aluminium and Zinc), regenerative heat exchangers, slag ladles (for non-basic slags), fire bars and hearths tunnel kiln conveyors, hot plates, components of ovens, kilns and furnaces and plant and apparatus for handling certain corrosive chemicals, all constructed at least in part of an iron/phosphorus alloy as aforesaid.
• iron/phosphorus alloys as aforesaid are of value in the construction of mills and grinding equipment.
• a rotary mill may be constructed containing cast balls, rods or other articles formed from an iron/ phosphorus alloy as aforesaid.
• our invention provides alloys which are of value in constructing articles according to our invention comprising a major proportion of iron, part of which is present as the chemically free metal, from 45-10% by weight of phosphorus and a minor proportion of other elements commonly present in cast iron and in ferrophosphorus.
• alloys according to our invention or for use in the construction of articles according to our invention, contain more than 5% and most preferably more than 6% by weight of phosphorus, especially for applications in which resistance to high temperature scal ing over long periods is an important factor. For such applications alloys containing 69% of phosphorus are preferred. However, if greater strength or ease of casting is required, the phosphorus content may be reduced, giving alloys having for example 2.55% by weight of phosphorus. Desirably the alloys contain elements other than iron and phosphorus in a total proportion of less than 10% by weight, e.g. 2 to 7% by weight. Other elements which may be present include carbon, silicon, vanadium, chromium, manganese, cobalt and nickel.
• the silicon content is normally from 1 to 5.5% by weight and preferably no greater than will be provided by incorporating ferrophosphorus into a conventional grey iron casting e.g. 2 to 3%.
• the total proportion of silicon and phosphorus is less than 15 by weight, since at higher proportions the composition ceases to be an alloy of free iron and consists of a mixture of iron phosphides and/or iron silicides.
• the carbon content is preferably less than 5% by weight and most preferably less than 3%. Typically the amount of carbon is 1.5 to 2.5% by weight. Other compatible metals are commonly present in a proportion of 0 to 5% by weight.
• the alloys according to our invention may conveniently be prepared by adding ferrophosphorus to a molten iron or other ferrous alloy containing a major proportion of iron, or by melting iron and ferrophosphorus together. Alternatively elemental phosphorus may be added direct to a molten iron or ferrous alloy.
• the iron may conveniently be a melt suitable for the preparation of conventional cast iron, e.g. grey cast iron.
• ferrophosphorus refers to the iron/ phosphorus composition obtained as a by-prodnot of the electric reduction process for making phosphorus and comprising a mixture of iron phosphides.
• ferrophosphorus contains a major proportion of iron, from 20-30% of phosphorus and other elements (such as silicon, vanadium, chromium, manganese, cobalt and nickel) in a total proportion of less than 15
• the novel alloys of our invention are of particular value in the construction of storage heaters.
• Our US. Pat. No. 3,381,113 proposed the use of ferrophosphorus for constructing storage heaters, it having been discovered that ferrophosphorus has an unusually high heat capacity.
• ferrophosphorus has the disadvantage that, owing to its brittleness and low crushing strength, it is difficult to construct sufficiently strong self supporting castings for ordinary use in storage heater cores. Hitherto it has proved necessary to sinter granular ferrophosphorus with a ceramic binder such as fireclay to provide a material sufiiciently strong for such uses. This has the disadvantage that the resulting composite has a markedly reduced heat capacity, so that the heater reservoirs must be unduly bulky to provide adequate heat storage: this has been an important drawback especially for domestic room heaters. Ceramic materials and composites also have a low thermal conductivity, which inhibits storage and recovery of heat.
• Cast iron It has also been proposed to employ ordinary cast iron for constructing storage heaters. Cast iron however suffers from two serious disadvantages Firstly, it has an undesirably low heat capacity. Secondly, cast iron undergoes oxidative corrosion and scaling at the normal operating temperatures of storage heaters. This corrosion limits the useful temperature range over which it is possible to use cast iron.
• the balance consisted, in each case, substantially of iron, with less than 0.2% of other elements.
• the samples were all readily cast into blocks which exhibited good resistance to high temperature oxidation, and were particularly suitable for use in constructing storage heater cores.
• EXAMPLE 10 The alloy of Example 8 was compared against the three most commonly used heat storage materials.
• alloys according to the present invention to construct etficient domestic storage heaters which are slenderer and less bulky than those hitherto available. Additionally, it has been found that the alloys of our invention possess greatly improved resistance to high temperature corrosion. This is surprising since they contain chemically free iron and would therefore have been expected to corrode readily.
• novel alloys of this invention are substantially stronger than ferrophosphorus and may readily be cast to form self supporting cores for storage heaters. They have significantly greater thermal conductivity than fireclay or the ceramic compositions containing granular ferrophosphorus employed hitherto. Alloys according to our invention may be used for constructing thermal reservoirs in any of the Ways described and illustrated in U.S. Pat. No. 3,381,113.
• the invention also provides composites of an alloy according to the invention sintered with a ceramic material.
• ferrous alloy is an alloy of cast iron with ferrophosphorus.
• An improved storage heater according to claim 2 wherein the proportion of carbon is from 1.5 to 2.5% by weight.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
• Heat Treatment Of Steel (AREA)

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Citations (8)

• 1966
  • 1966-05-09 GB GB56606/66A patent/GB1193061A/en not_active Expired
• 1967
  • 1967-04-25 US US633397A patent/US3533758A/en not_active Expired - Lifetime
  • 1967-04-27 DE DE19671558439 patent/DE1558439B1/de active Pending
  • 1967-05-05 AT AT420067A patent/AT294163B/de not_active IP Right Cessation
  • 1967-05-05 CH CH636467A patent/CH497536A/de not_active IP Right Cessation
  • 1967-05-08 NL NL6706398A patent/NL6706398A/xx unknown
  • 1967-05-08 BE BE698133D patent/BE698133A/xx unknown
  • 1967-05-08 LU LU53616D patent/LU53616A1/xx unknown

Patent Citations (8)

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